Uses of high mullite index calcined kaolin

Abstract

Disclosed are methods of making calcined kaolin having a high mullite content involving heating to certain temperatures. Also disclosed are systems for making the calcined kaolin having a high mullite content and polymer composites containing the calcined kaolin having a high mullite content. The present calcined kaolin having a high mullite content is particularly useful in making polymer composites. The polymer composites may be used in electrical cable.

1. A polymer composite, comprising (a) from about 25% to about 99.9% by weight of a polymer matrix; and (b) from about 0.1% to about 75% by weight of a calcined kaolin having a high mullite content of at least 25% by weight with a 250 g dry flow rate of less than about 100 seconds. 
     
     
       2. The polymer composite of  claim 1  wherein said calcined kaolin having a high mullite content contains at least about 30% by weight of said mullite. 
     
     
       3. The polymer composite of  claim 1  wherein said calcined kaolin having a high mullite content contains at least about 40% by weight of said mullite. 
     
     
       4. The polymer composite of  claim 1  comprising (a) from about 50% to about 99.5% by weight of a polymer matrix; and (b) from about 0.5% to about 50% by weight of a calcined kaolin having a high mullite content of at least 25% with a 250 g dry flow rate of less than about 100 seconds. 
     
     
       5. The polymer composite of  claim 1  comprising (a) from about 75% to about 99% by weight of a polymer matrix; and (b) from about 1% to about 25% by weight of a calcined kaolin having a high, mullite content of at least 25% with a 250 g dry flow rate of less than about 100 seconds. 
     
     
       6. The polymer composite of  claim 1  wherein said calcined kaolin having high mullite content has a particle size distribution wherein at least about 60% by weight of said kaolin particles have an average particle size of 2 microns or less, at least about 30% by weight of said kaolin particles have an average particle size of 1 micron or less, and at least about 5% by weight of said kaolin particles have an average particle size of 0.5 micron or less. 
     
     
       7. The polymer composite of  claim 1  wherein said calcined kaolin having high mullite content has a particle size distribution wherein at least about 65% by weight of said kaolin particles have an average particle size of 2 microns or less, at least about 40% by weight of said kaolin particles have an average particle size of 1 micron or less, and at least about 10% by weight of said kaolin particles have an average particle size of 0.5 micron or less. 
     
     
       8. The polymer composite of  claim 1  wherein said calcined kaolin having high mullite content has a particle size distribution wherein at least about 75% by weight of said kaolin particles have an average particle size of 2 microns or less, at least about 50% by weight of said kaolin particles have an average particle size of 1 micron or less, and at least about 12% by weight of said kaolin particles have an average particle size of 0.5 micron or less. 
     
     
       9. The polymer composite of  claim 1  wherein said calcined kaolin having a high mullite content has a dry flow rate of less than about 80 seconds. 
     
     
       10. The polymer composite of  claim 1  wherein said calcined kaolin having a high mullite content has a dry flow rate of less than about 65 seconds. 
     
     
       11. The polymer composite of  claim 1  wherein said calcined kaolin having a high mullite content has a dry flow rate of less than about 40 seconds. 
     
     
       12. The polymer composite of  claim 1  having improved mechanical and/or thermal properties. 
     
     
       13. The polymer composite of  claim 12  wherein said improved mechanical and/or thermal properties is selected from the group consisting of tensile strength, flexural strength, elasticity modulus, impact strength, ductility, heat distortion temperature, electrical insulation properties, temperature insulation properties, flow characteristics, flame retardancy, dimensional stability, hardness and creep characteristics. 
     
     
       14. The polymer composite of  claim 1  further comprising additional additives selected from the group consisting of fillers, property enhancers, pigments, and surfactants.